178 research outputs found
Broadly tunable (440-670 nm) solid-state organic laser with disposable capsules
An innovative concept of thin-film organic solid-state laser is proposed,
with diffraction-limited output and a broad tuning range covering the visible
spectrum under UV optical pumping. The laser beam is tunable over 230 nm, from
440 to 670 nm, with a 3 nm full width at half maximum typical spectral width.
The structure consists of a compact fixed bulk optical cavity, a polymeric
intracavity etalon for wavelength tuning, as well as five different disposable
glass slides coated with a dye-doped polymer film, forming a very simple and
low-cost gain medium. The use of interchangeable/disposable "gain capsules" is
an alternative solution to photodegradation issues, since gain chips can be
replaced without realignment of the cavity. The laser lifetime of a single chip
in ambient conditions and without encapsulation was extrapolated to be around
107 pulses at a microjoule energy-per-pulse level
White Organic Light-Emitting Diodes with fine chromaticity tuning via ultrathin layer position shifting
Non-doped white organic light-emitting diodes using an ultrathin
yellow-emitting layer of rubrene (5,6,11,12-tetraphenylnaphtacene) inserted on
either side of the interface between a hole-transporting NPB
(4,4'-bis[N-(1-naphtyl)-N-phenylamino]biphenyl) layer and a blue-emitting DPVBi
(4,4'-bis(2,2'-diphenylvinyl)-1,1'-biphenyl) layer are described. Both the
thickness and the position of the rubrene layer allow fine chromaticity tuning
from deep-blue to pure-yellow via bright-white with CIE coordinates (x= 0.33,
y= 0.32), a external quantum efficiency of 1.9%, and a color rendering index of
70. Such a structure also provides an accurate sensing tool to measure the
exciton diffusion length in both DPVBi and NPB (8.7 and 4.9 nm respectively)
Tunable Ultraviolet Vertically-emitting Organic Laser
International audienceA solid-state organic thin-film laser with intracavity frequency doubling is reported. Tunable ultraviolet emission from 309 to 322 nm is achieved from a vertical external cavity surface-emitting organic laser, with 2 % efficiency (1 µJ at 315 nm). The laser comprises a polymethyl(methacrylate) layer doped with Rhodamine 640, spun-cast onto a plane mirror, a remote concave mirror, a nonlinear crystal and a dichroic separator. The output is spectrally narrow (<0.5 nm FWHM) and tunable through phase-matching selection of the fundamental radiation lasing modes. These results highlight a low-cost and portable alternative to tunable UV laser sources, useful for spectroscopic applications
Highly-efficient, diffraction-limited laser emission from a Vertical External Cavity Surface-emitting Organic Laser
We report on a solid-state laser structure being the organic counterpart of
the Vertical External-Cavity Surface-Emitting Laser (VECSEL) design. The gain
medium is a poly (methyl methacrylate) film doped with Rhodamine 640,
spin-casted onto the High-Reflectivity mirror of a plano-concave resonator.
Upon pumping by 7-ns pulses at 532 nm, a diffraction-limited beam (M^2=1) was
obtained, with a conversion efficiency of 43%; higher peak powers (2kW) could
be attained when resorting to shorter (0.5 ns) pump pulses. The spectrum was
controlled by the thickness of the active layer playing the role of an
intracavity etalon; tunability is demonstrated over up to 20 nm
Characterization of Preoperative, Postsurgical, Acute and Chronic Pain in High Risk Breast Cancer Patients
Funding: The Ketorolac in Breast Cancer trial has been supported by the Anticancer Fund, the Belgian Society of Anaesthesia and Resuscitation, the Fondation Saint-Luc, and the Commission du Patrimoine of the Université catholique de Louvain, Cliniques universitaires Saint-Luc. Acknowledgments: Membership of the KBCt Group, Aline van Maanen, Gauthier Bouche, Alain Dekleermaker, Francois P Duhoux, Marc De Kock, Martine Berliere, Pierre Coulie, Jan Decloedt, Jean-Edouard Guillaume, Marc Ledent, Jean-Pascal Machiels, Véronique Mustin, Walter Swinnen, Lionel Vander Essen, and Jean-Christophe Verougstraete.Peer reviewedPublisher PD
Influencing users towards better passwords: Persuasive cued click-points
Usable security has unique usability challenges because the need for security often means that standard human-computerinteraction approaches cannot be directly applied. An important usability goal for authentication systems is to support users in selecting better passwords, thus increasing security by expanding the effective password space. In click-based graphical passwords, poorly chosen passwords lead to the emergence of hotspots ' portions of the image where users are more likely to select click-points, allowing attackers to mount more successful dictionary attacks. We use persuasion to influence user choice in click-based graphical passwords, encouraging users to select more random, and hence more secure, click-points. Our approach is to introduce persuasion to the Cued Click-Points graphical password scheme (Chiasson, van Oorschot, Biddle, 2007). Our resulting scheme significantly reduces hotspots while still maintaining its usability
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